this video we just showed from the assad regime, shown on syrian state television. want to show it again. it's supposedly a victim suffering from a chemical weapons attack. no one shows any physical signs of injury, no convulsions, no vomiting. at least three experts on chemical weapons say that judging from what they see here, it doesn't seem like a chemical weapons attack. knowing what you know about these type of agents and their effect on humans, do you agree? >> you know, it's difficult to tell without examining the patients. and you need sophisticated equipment to do that. a lot of the symptoms you're seeing in these patients could be caused by insecticide, for instance. any organophosphate which sarin is, but the fact that so few people have died or if any have died tells me that this probably wasn't a sarin attack but we can't rule out some sort of diluted chemical had been used. >> the regime is saying it's the rebels using chemicals. if it was something like a diluted chemical, dispersal agent or something, would that be crossing the red line? >> sure. loo